NASA’s new moon rocket sprang another dangerous fuel leak Saturday, forcing launch controllers to call off their second attempt to send a crew capsule into lunar orbit with test dummies. The first attempt earlier in the week was also marred by escaping hydrogen, but those leaks were elsewhere on the 322-foot (98-meter) rocket, the most powerful ever built by NASA. Launch director Charlie Blackwell-Thompson and her team tried to plug Saturday’s leak the way they did the last time: stopping and restarting the flow of super-cold liquid hydrogen in hopes of removing the gap around a seal in the supply line. They tried that twice, in fact, and also flushed helium through the line. But the leak persisted. Blackwell-Thompson finally halted the countdown after three to four hours of futile effort. THIS IS A BREAKING NEWS UPDATE. AP’s earlier story follows below. CAPE CANAVERAL, Fla.  (AP) — NASA's new moon rocket sprang another hazardous leak Saturday, as the launch team began fueling it for liftoff on a test flight that must go well before astronauts climb aboard. For the second time this week, the launch team began loading nearly 1 million gallons of fuel into the 322-foot (98-meter) rocket, the most powerful ever built by NASA. Monday’s attempt was halted by a bad engine sensor and leaking fuel. As the sun rose, an over-pressure alarm sounded and the tanking operation was briefly halted, but no damage occurred and the effort resumed. But minutes later, hydrogen fuel began leaking from the engine section at the bottom of the rocket. NASA halted the operation, while engineers scrambled to plug what was believed to be a gap around a seal in the supply line. The countdown clocks continued ticking toward an afternoon liftoff; NASA had two hours Saturday to get the rocket off. NASA wants to send the crew capsule atop the rocket around the moon, pushing it to the limit before astronauts get on the next flight. If the five-week demo with test dummies succeeds, astronauts could fly around the moon in 2024 and land on it in 2025. People last walked on the moon 50 years ago. Forecasters expected generally favorable weather at Kennedy Space Center, especially toward the end of the two-hour afternoon launch window. On Monday, hydrogen fuel escaped from elsewhere in the rocket. Technicians tightened up the fittings over the past week, but launch director Charlie Blackwell-Thompson stressed that she wouldn't know whether everything was tight until Saturday's fueling. Read: NASA scrubs launch of new moon rocket after engine problem Even more of a problem on Monday, a sensor indicated one of the rocket's four engines was too warm, but engineers later verified it actually was cold enough. The launch team planned to ignore the faulty sensor this time around and rely on other instruments to ensure each main engine was properly chilled. Before igniting, the main engines need to be as frigid as the liquid hydrogen fuel flowing into them at minus-420 degrees Fahrenheit (minus-250 degrees Celsius). If not, the resulting damage could lead to an abrupt engine shutdown and aborted flight. Mission managers accepted the additional risk posed by the engine issue as well as a separate problem: cracks in the rocket's insulating foam. But they acknowledged other problems — like fuel leaks — could prompt yet another delay. That didn't stop thousands from jamming the coast to see the Space Launch System rocket soar. Local authorities expected massive crowds because of the long Labor Day holiday weekend. The $4.1 billion test flight is the first step in NASA's Artemis program of renewed lunar exploration, named after the twin sister of Apollo in Greek mythology. Twelve astronauts walked on the moon during NASA’s Apollo program, the last time in 1972. Artemis — years behind schedule and billions over budget — aims to establish a sustained human presence on the moon, with crews eventually spending weeks at a time there. It's considered a training ground for Mars.    

NASA aimed for a Saturday launch of its new moon rocket, after fixing fuel leaks and working around a bad engine sensor that foiled the first try. The inaugural flight of the 322-foot (98-meter) rocket — the most powerful ever built by NASA — was delayed late in the countdown Monday. The Kennedy Space Center clocks started ticking again as managers expressed confidence in their plan and forecasters gave favorable weather odds. Atop the rocket is a crew capsule with three test dummies that will fly around the moon and back over the course of six weeks — NASA’s first such attempt since the Apollo program 50 years ago. NASA wants to wring out the spacecraft before strapping in astronauts on the next planned flight in two years. NASA Administrator Bill Nelson said he’s more confident going into this second launch attempt, given everything engineers learned from the first try. Also read: Fuel leak interrupts launch countdown of NASA moon rocket So is astronaut Jessica Meir, who’s on NASA’s short list for one of the initial moon crews. “We’re all excited for this to go, but the most important thing is that we go when we’re ready and we get it right, because the next missions will have humans on board. Maybe me, maybe my friends,” Meir told The Associated Press on Friday. The engineers in charge of the Space Launch System rocket insisted Thursday evening that all four of the rocket’s main engines were good and that a faulty temperature sensor caused one of them to appear as though it were too warm Monday. The engines need to match the minus-420 degrees Fahrenheit (minus-250 degrees Celsius) of the liquid hydrogen fuel at liftoff, otherwise they could be damaged and shut down in flight. “We have convinced ourselves without a shadow of a doubt that we have good-quality liquid hydrogen going through the engines,” said John Honeycutt, the rocket’s program manager. Once fueling begins Saturday morning, the launch team will perform another engine test — this time earlier in the countdown. Even if that suspect sensor indicates the one engine is too warm, other sensors can be relied on to ensure everything is working correctly and to halt the countdown if there’s a problem, Honeycutt told reporters. NASA could not perform that kind of engine test during dress rehearsals earlier this year because of leaking fuel. More fuel leaks cropped up Monday; technicians found some loose connections and tightened them. The engine-temperature situation adds to the flight’s risk, as does another problem that cropped up Monday: cracks in the foam insulation of the rocket. If any foam pieces break off at liftoff, they could strike the strap-on boosters and damage them. Engineers consider the likelihood of that happening low and have accepted these slight additional risks. “This is an extremely complicated machine and system. Millions of parts,” NASA’s chief, Nelson, told the AP. “There are, in fact, risks. But are those risks acceptable? I leave that to the experts. My role is to remind them you don’t take any chances that are not acceptable risk.”   The $4.1 billion test flight is NASA’s first step in sending astronauts around the moon in 2024 and landing them on the surface in 2025. Astronauts last walked on the moon in 1972.

NASA will try again Saturday to launch its new moon rocket on a test flight, after engine trouble halted the first countdown this week. Managers said Tuesday they are changing fueling procedures to deal with the issue. A bad sensor also could be to blame for Monday’s scrapped launch, they noted. The 322-foot (98-meter) rocket — the most powerful ever built by NASA — remains on its pad at Kennedy Space Center with an empty crew capsule on top. The Space Launch System rocket will attempt to send the capsule around the moon and back. No one will be aboard, just three test dummies. If successful, it will be the first capsule to fly to the moon since NASA’s Apollo program 50 years ago. Read: NASA scrubs launch of new moon rocket after engine problem Proceeding toward a Saturday launch will provide additional insight, even if the problem reappears and the countdown is halted again, said NASA’s rocket program manager, John Honeycutt. That’s better “than us sitting around scratching our heads, was it good enough or not.” “Based on what I’ve heard from the technical team today, what we need to do is continue to pore over the data and polish up our plan on putting the flight rationale together,” he said. During Monday’s launch attempt, readings showed that one of the four main engines in the rocket’s core stage could not be chilled sufficiently prior to the planned ignition at liftoff. It appeared to be as much as 40 degrees Fahrenheit (5 degrees Celsius) warmer than the desired minus-420 degrees Fahrenheit (minus-250 degrees Celsius), the temperature of the hydrogen fuel, according to Honeycutt. The three other engines came up just a little short. All of the engines appear to be fine, according to Honeycutt. The chilling operation will be conducted a half-hour earlier for Saturday afternoon’s launch attempt, once fueling begins that morning. Honeycutt said the timing of this engine chilldown was earlier during successful testing last year, and so performing it sooner may do the trick. Read: Facebook parent settles suit in Cambridge Analytica scandal Honeycutt also questioned the integrity of one engine sensor, saying it might have provided inaccurate data Monday. To change that sensor, he noted, would mean hauling the rocket back into the hangar, resulting in weeks of delay. Already years behind schedule, the $4.1 billion test flight is the opening shot in NASA’s Artemis moon-exploration program, named after the twin sister of Apollo in Greek mythology. Astronauts could strap in as soon as 2024 for a lap around the moon and actually attempt a lunar landing in 2025.

A fuel leak interrupted NASA's launch countdown for its new moon rocket early Monday, reappearing in the same place that saw seepage during a dress rehearsal back in the spring. Launch controllers halted the tanking operation, which already was running an hour late because of thunderstorms offshore. They slowly resumed the process to confirm that it was, indeed, a hydrogen fuel leak and not faulty sensors, but alarms forced another temporary pause as precious minutes in the countdown ticked away. The 322-foot (98-meter) rocket is the most powerful ever built my NASA, out-muscling even the Saturn V that carried astronauts to the moon a half-century ago. This test flight, if successful, would put a crew capsule into lunar orbit for the first time in 50 years. No astronauts were inside the Orion capsule atop the rocket at NASA's Kennedy Space Center. Instead, three test dummies were strapped in for the lunar-orbiting mission, expected to last six weeks. Even with no one on board, thousands of people jammed the coast to see the Space Launch System, or SLS, rocket soar. Vice President Kamala Harris flew into Orlando with her husband, but had yet to make the hourlong drive to Cape Canaveral for the planned liftoff. The next launch attempt wouldn’t be until Friday at the earliest. Read: NASA tests new moon rocket, 50 years after Apollo Hydrogen fuel leaks marred NASA's countdown test back in April, prompting a slew of repairs. The demo was repeated with more success in June, but that, too, experienced some leakage. Managers said they would not know for certain whether the fixes were good until attempting to load the rocket's tanks with nearly 1 million gallons of super-cold fuel on Monday. Launch director Charlie Blackwell-Thompson and her team also had to deal with a communication issue involving the Orion capsule. Engineers scrambled to understand an 11-minute delay in the communication lines between Launch Control and Orion that cropped up late Sunday. Although the problem had cleared by Monday morning, NASA needed to know why it occurred before committing to launch. This first flight of NASA's 21st-century moon-exploration program, named Artemis after Apollo's mythological twin sister, is years overdue. Repeated delays have led to billions in budget overruns; this demo alone costs $4.1 billion. Assuming the test goes well, astronauts would climb aboard for the second flight and fly around the moon and back as soon as 2024. A two-person lunar landing could follow by the end of 2025. NASA is targeting the moon's south pole. During Apollo, 12 astronauts landed on the moon from 1969 through 1972, with stays of no more than a few days. NASA is looking to establish a lunar base during Artemis, with astronauts rotating in and out for weeks at a time. The next step would be Mars, possibly in the late 2030s or early 2040s.

Years late and billions over budget, NASA’s new moon rocket makes its debut next week in a high-stakes test flight before astronauts get on top. The 322-foot (98-meter) rocket will attempt to send an empty crew capsule into a far-flung lunar orbit, 50 years after NASA’s famed Apollo moonshots. If all goes well, astronauts could strap in as soon as 2024 for a lap around the moon, with NASA aiming to land two people on the lunar surface by the end of 2025. Liftoff is set for Monday morning from NASA’s Kennedy Space Center. The six-week test flight is risky and could be cut short if something fails, NASA officials warn. “We’re going to stress it and test it. We’re going make it do things that we would never do with a crew on it in order to try to make it as safe as possible,” NASA Administrator Bill Nelson told The Associated Press on Wednesday. The retired founder of George Washington University’s space policy institute said a lot is riding on this trial run. Spiraling costs and long gaps between missions will make for a tough comeback if things go south, he noted. Also read: NASA’s new telescope shows star death, dancing galaxies “It is supposed to be the first step in a sustained program of human exploration of the moon, Mars, and beyond,” said John Logsdon. “Will the United States have the will to push forward in the face of a major malfunction?” The price tag for this single mission: more than $4 billion. Add everything up since the program’s inception a decade ago until a 2025 lunar landing, and there’s even more sticker shock: $93 billion. Here’s a rundown of the first flight of the Artemis program, named after Apollo’s mythological twin sister. ROCKET POWER The new rocket is shorter and slimmer than the Saturn V rockets that hurled 24 Apollo astronauts to the moon a half-century ago. But it’s mightier, packing 8.8 million pounds (4 million kilograms) of thrust. It’s called the Space Launch System rocket, SLS for short, but a less clunky name is under discussion, according to Nelson. Unlike the streamlined Saturn V, the new rocket has a pair of strap-on boosters refashioned from NASA’s space shuttles. The boosters will peel away after two minutes, just like the shuttle boosters did, but won’t be fished from the Atlantic for reuse. The core stage will keep firing before separating and crashing into the Pacific in pieces. Two hours after liftoff, an upper stage will send the capsule, Orion, racing toward the moon. MOONSHIP NASA’s high-tech, automated Orion capsule is named after the constellation, among the night sky’s brightest. At 11 feet (3 meters) tall, it’s roomier than Apollo’s capsule, seating four astronauts instead of three. For this test flight, a full-size dummy in an orange flight suit will occupy the commander’s seat, rigged with vibration and acceleration sensors. Two other mannequins made of material simulating human tissue — heads and female torsos, but no limbs — will measure cosmic radiation, one of the biggest risks of spaceflight. One torso is testing a protective vest from Israel. Unlike the rocket, Orion has launched before, making two laps around Earth in 2014. This time, the European Space Agency’s service module will be attached for propulsion and solar power via four wings.   FLIGHT PLAN Orion’s flight is supposed to last six weeks from its Florida liftoff to Pacific splashdown, twice as long as astronaut trips in order to tax the systems. It will take nearly a week to reach the moon, 240,000 miles (386,000 kilometers) away. After whipping closely around the moon, the capsule will enter a distant orbit with a far point of 38,000 miles (61,000 kilometers). That will put Orion 280,000 miles (450,000 kilometers) from Earth, farther than Apollo. The big test comes at mission’s end, as Orion hits the atmosphere at 25,000 mph (40,000 kph) on its way to a splashdown in the Pacific. The heat shield uses the same material as the Apollo capsules to withstand reentry temperatures of 5,000 degrees Fahrenheit (2,750 degrees Celsius). But the advanced design anticipates the faster, hotter returns by future Mars crews. HITCHHIKERS Besides three test dummies, the flight has a slew of stowaways for deep space research. Ten shoebox-size satellites will pop off once Orion is hurtling toward the moon. The problem is these so-called CubeSats were installed in the rocket a year ago, and the batteries for half of them couldn’t be recharged as the launch kept getting delayed. NASA expects some to fail, given the low-cost, high-risk nature of these mini satellites. The radiation-measuring CubeSats should be OK. Also in the clear: a solar sail demo targeting an asteroid. In a back-to-the-future salute, Orion will carry a few slivers of moon rocks collected by Apollo 11′s Neil Armstrong and Buzz Aldrin in 1969, and a bolt from one of their rocket engines, salvaged from the sea a decade ago. Aldrin isn’t attending the launch, according to NASA, but three of his former colleagues will be there: Apollo 7′s Walter Cunningham, Apollo 10′s Tom Stafford and Apollo 17′s Harrison Schmitt, the next-to-last man to walk on the moon. APOLLO VS. ARTEMIS More than 50 years later, Apollo still stands as NASA’s greatest achievement. Using 1960s technology, NASA took just eight years to go from launching its first astronaut, Alan Shepard, and landing Armstrong and Aldrin on the moon. By contrast, Artemis already has dragged on for more than a decade, despite building on the short-lived moon exploration program Constellation. Twelve Apollo astronauts walked on the moon from 1969 through 1972, staying no longer than three days at a time. For Artemis, NASA will be drawing from a diverse astronaut pool currently numbering 42 and is extending the time crews will spend on the moon to at least a week. The goal is to create a long-term lunar presence that will grease the skids for sending people to Mars. NASA’s Nelson, promises to announce the first Artemis moon crews once Orion is back on Earth. WHAT’S NEXT There’s a lot more to be done before astronauts step on the moon again. A second test flight will send four astronauts around the moon and back, perhaps as early as 2024. A year or so later, NASA aims to send another four up, with two of them touching down at the lunar south pole. Orion doesn’t come with its own lunar lander like the Apollo spacecraft did, so NASA has hired Elon Musk’s SpaceX to provide its Starship spacecraft for the first Artemis moon landing. Two other private companies are developing moonwalking suits. The sci-fi-looking Starship would link up with Orion at the moon and take a pair of astronauts to the surface and back to the capsule for the ride home. So far, Starship has only soared six miles (10 kilometers). Musk wants to launch Starship around Earth on SpaceX’s Super Heavy Booster before attempting a moon landing without a crew. One hitch: Starship will need a fill-up at an Earth-orbiting fuel depot, before heading to the moon.

NASA's latest attempt to fuel its huge moon rocket for a countdown test was thwarted Thursday by a hazardous hydrogen leak, the latest in a series of vexing equipment trouble. The launch team had just begun loading fuel into the core stage of the rocket when the leak cropped up. This was NASA's third shot at a dress rehearsal, a required step ahead of a test flight to the moon. This time, the launch team managed to load some super-cold liquid hydrogen and oxygen into the core stage of the 30-story Space Launch System rocket, but fell far short of the full amount. Liquid hydrogen is extremely hazardous, with officials noting that the systems had been checked for leaks prior to the test. Also read: China launches new satellite for Earth observation Technicians deliberately left the smaller upper stage empty, after discovering a bad valve last week. The helium valve inside the upper stage cannot be replaced until the rocket is back in its hangar at Kennedy Space Center. Two previous countdown attempts were marred by balky fans and a large hand-operated valve that workers mistakenly left closed at the pad last week. Officials said via Twitter that they're assessing their next steps. Also read: Researchers print 3D cardiac tissue capable of sustaining pulses for over 6 months NASA had been targeting June for the launch debut of the 322-foot (98-meter) SLS rocket. The empty Orion capsule on top will be sent on a four- to six-week mission around the moon and back. Astronauts will strap in for the second test flight around the moon, planned for 2024. That would be followed as early as 2025 with the first lunar landing by astronauts since 1972. NASA plans to announce the crews for these two missions this summer.

NASA completed an engine test firing of its moon rocket Thursday, after the first attempt in January ended prematurely.